Seperate ROS and low level driver better.

The seperation is not perfect, but the driver is functional.

Signed-off-by: Karl Damkjær Hansen <kdh@es.aau.dk>
Thread driver loop from davinci driver itself.

Previously the ROS part created the thread, now the lower level
driver does this.

Signed-off-by: Karl Damkjær Hansen <kdh@es.aau.dk>
Fix the thread hanging when exiting the driver.

The call to read_some from the socket blocks. So if no data is
received, the thread does not reach the interrupt point, and it hangs
until the process is killed.

Signed-off-by: Karl Damkjær Hansen <kdh@es.aau.dk>